Single riser/single capillary blood viscometer using mass detection or column height detection

ABSTRACT

An apparatus and method for determining the viscosity of the circulating blood of a living being over plural shear rates caused by a decreasing pressure differential by monitoring the changing weight of the blood, or the changing level of a column of blood over time. The apparatus and method utilize a riser, a capillary tube, a collector and a mass detector, such as a precision balance or a load cell, for monitoring the changing weight of a sample of fluid that flows through these components under the influence of the decreasing pressure differential; alternatively, the apparatus and method use a column level detector to monitor the changing level of the column of blood over time.

RELATED APPLICATIONS

[0001] This application is a Continuation-In-Part of application Ser.No. 09/789,350, filed Feb. 21, 2001, entitled Mass Detection CapillaryViscometer, which in turn is based on Provisional Application Serial No.60/228,612 filed Aug. 29, 2000 entitled MASS DETECTION CAPILLARYVISCOMETER. This application is also a Continuation-in-Part ofapplication Ser. No. 09/573,267 filed May 18, 2000, entitled DUALRISER/SINGLE CAPILLARY VISCOMETER. The entire disclosures of all theabove applications are incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] A capillary viscometer is commonly used because of its inherentfeatures such as simplicity, accuracy, similarity to process flows likeextrusion dies, no free surface, etc. Viscous flow in capillaryviscometry is firmly established both theoretically and experimentally.C. W. Macosko, Rheology: Principles, Measurements, and Applications(VCH, 1993). In fact, the capillary viscometer was the first viscometerand this device remains the most common for measuring viscosity forpolymer solutions and other non-Newtonian fluids. However, most existingcapillary viscometers produce viscosity measurement a shear rate at atime. In the case of Newtonian fluids the observation of the rate offlow at a single pressure drop is sufficient to define the flowbehavior. However, in the case of non-Newtonian fluids, viscositymeasurements need to be performed over a range of shear rates. In orderto measure viscosity over a range of shear rates, it is necessary torepeat the measurement by varying either the driving pressure head orthe capillary tube diameter, which leads to a time-consuming measurementrequiring intensive labor. Hence, these methods are not suited formeasuring the rheology of polymer fluids that may exhibitshear-dependent viscosities. Furthermore, application of such techniquesoften requires relatively large volumes of the test fluids. Therefore,there has been a need to develop a simple and labor-free viscometerwhich can measure the viscosity of fluids over shear rates at a time.

[0003] In U.S. Pat. Nos. 6,019,735 (Kensey et al.) and U.S. Pat. No.6,077,234 (Kensey et al.), which are assigned to the same Assignee,namely Visco Technologies, Inc., of the present invention, there isdisclosed a scanning-capillary-tube viscometer for measuring theviscosity of a fluid, e.g., circulating blood of a living being. Amongother things, this scanning capillary tube viscometer discloses anapparatus that monitors the changing height of a column of fluid versustime in a riser that is in fluid communication with a living being'scirculating blood. A further improvement of this type of scanningcapillary tube viscometer is disclosed in application Ser. No.09/439,735 entitled DUAL RISER/SINGLE CAPILLARY VISCOMETER, which isassigned to the same Assignee as the present invention, namely, ViscoTechnologies, Inc. and whose entire disclosure is incorporated byreference herein. In that application, a U-shaped tube structure isutilized that generates a falling and rising column of test fluid thatis driven by a decreasing pressure differential for moving these columnsof fluid through a plurality of shear rates, which is necessary fornon-Newtonian fluid (e.g., blood) viscosity determinations. Such anapparatus can produce viscosity data in a low shear range (e.g.,approximately 0.02 s⁻¹).

[0004] However, there is a need for an alternative mechanism ofmonitoring the changing column of fluid over time, such as detecting thechanging mass of the column of fluid, as set forth in the presentapplication. The key principle of the mass-detection-capillaryviscometer is that both flow rate and pressure drop at a capillary tubecan be determined by a single measurement of collected fluid massvariation with time using a load cell. Thus, there also remains a needto develop a viscosity determination in a quasi-steady capillary flowand to measure the viscosity of non-Newtonian fluids (e.g., polymersolutions, circulating blood of a living being, etc.) over a range ofshear rates.

SUMMARY OF THE INVENTION

[0005] An apparatus for determining the viscosity of the circulatingblood of a living being over plural shear rates using a decreasingpressure differential. The apparatus comprises: a lumen (e.g., a risertube) being positioned at an angle to a horizontal reference greaterthan zero degrees, wherein the lumen comprises a first end and a secondend and wherein the first end is exposed to atmospheric pressure andwherein the lumen comprises a first known dimension (e.g., the diameterof the lumen); a flow restrictor (e.g., a capillary tube) having aninlet and an outlet wherein the outlet is arranged to deliver any bloodthat passes therethrough to a collector, and wherein the flow restrictorincludes some known dimensions (e.g., the length and diameter of theflow restrictor); a valve coupled to the vascular system of the livingbeing at a first port and wherein the valve comprises a second portcoupled to the second end and a third port is coupled to the inlet; asensor for detecting the movement of the blood over time (e.g., a massdetector, a column level detector, etc.) through the apparatus andwherein the sensor generates data relating to the movement of the bloodover time; a processor, the valve to create a column of blood in thefirst lumen and the flow restrictor and to establish a pressuredifferential between the first end and the outlet, and wherein thecolumn of blood moves through the lumen and the flow restrictor at afirst shear rate caused by the pressure differential and wherein themovement of the column of blood causes the pressure differential todecrease from the first shear rate for generating the plural shearrates; and wherein the processor calculates the viscosity of the bloodbased on the data relating to the movement of the column of blood overtime, the first known dimension of the lumen and the some knowndimensions of the flow restrictor.

[0006] A method for determining the viscosity of the circulating bloodof a living being over plural shear rates caused by a decreasingpressure differential. The method comprises the steps of: (a) providinga lumen having a first end and a second end and positioned at an angleto a horizontal reference greater than zero degrees, and wherein thelumen has a first known dimension (e.g., the diameter of the lumen) andwherein the first end is exposed to atmospheric pressure; (b) divertinga portion of the circulating blood into the lumen through the second endto form a column of blood therein; (c) coupling an inlet of a flowrestrictor to the second end of the lumen to establish a pressuredifferential between the first end and the outlet and wherein the flowrestrictor has an outlet that is arranged to deliver any blood thatpasses therethrough to a collector and wherein the flow restrictor hassome known dimensions (e.g., the length and the diameter of the flowrestrictor); (d) controlling the column of blood to form a continuouscolumn of blood in the lumen and the flow restrictor, and wherein thecolumn of blood moves through the lumen and the flow restrictor at afirst shear rate caused by the pressure differential and wherein themovement of the column of blood causes the pressure differential todecrease from the first shear rate for generating the plural shearrates; (e) providing a sensor for detecting the movement of the columnof blood over time (e.g., a mass detector, a column level detector,etc.) as the column of blood moves and passes from the outlet into thecollector while maintaining the outlet submerged in blood that hascollected in the collector, and wherein the sensor generates dataregarding the movement; and (f) calculating the viscosity of the bloodbased on the generated data, the first known dimension and the someknown dimensions.

[0007] An apparatus for determining the viscosity of the circulatingblood of a living being over plural shear rates using a decreasingpressure differential. The apparatus comprises: a lumen (e.g., a risertube) being positioned at an angle to a horizontal reference greaterthan zero degrees, and wherein the lumen comprises a first end and asecond end and wherein the lumen also comprises a first known dimension(e.g., the diameter of the lumen); a flow restrictor (e.g., a capillarytube) having an inlet and an outlet wherein the outlet is arranged todeliver any blood that passes therethrough to a collector and whereinthe inlet is coupled to the second end and wherein the flow restrictorincludes some known dimensions (e.g., the length and diameter of theflow restrictor); a valve coupled to the vascular system of the livingbeing at a first port and wherein the valve comprises a second portcoupled to the first end; a sensor for detecting the movement of theblood over time (e.g., a mass detector, a column level detector, etc.)through the apparatus and wherein the sensor generates data relating tothe movement of the blood over time; a processor, coupled to the valveand the sensor wherein the processor is arranged to operate the valve tocreate a column of blood in the first lumen and the flow restrictor andto establish a pressure differential between the first end and theoutlet and wherein the column of blood moves through the lumen and theflow restrictor at a first shear rate caused by the pressuredifferential and wherein the movement of the column of blood causes thepressure differential to decrease from the first shear rate forgenerating the plural shear rates; and wherein the processor calculatesthe viscosity of the blood based on the data relating to the movement ofthe column of blood over time, the first known dimension of the lumenand the some known dimensions of the flow restrictor.

[0008] A method for determining the viscosity of the circulating bloodof a living being over plural shear rates caused by a decreasingpressure differential. The method comprises the steps of: (a) providinga lumen (e.g., a riser tube) having a first end and a second end andpositioned at an angle to a horizontal reference greater than zerodegrees and wherein the lumen has a first known dimension (e.g., thediameter of the lumen); (b) coupling an inlet of a flow restrictor(e.g., a capillary tube) to said second end and arranging an outlet ofthe flow restrictor to deliver any blood that passes therethrough to acollector and wherein the flow restrictor has some known dimensions(e.g., the length and diameter of the flow restrictor); (c) diverting aportion of the circulating blood into the lumen through the first end toform a column of blood in the lumen and the flow restrictor and toestablish a pressure differential between the first end and the outlet;(c) exposing the first end to atmospheric pressure to cause the columnof blood to move through the lumen and the flow restrictor, wherein themovement of the column of blood causes the pressure differential todecrease from the first shear rate for generating the plural shearrates; (d) providing a sensor for detecting the movement of the columnof blood over time (e.g., a mass detector, a column level detector,etc.) as the column of blood moves and passes from the outlet into thecollector while maintaining the outlet submerged in blood that hascollected in the collector and wherein the sensor generates dataregarding the movement; and (e) calculating the viscosity of the bloodbased on the generated data, the first known dimension and the someknown dimensions.

[0009] An apparatus for determining the viscosity of the circulatingblood of a living being over plural shear rates using a decreasingpressure differential. The apparatus comprises: a first lumen (a risertube) being positioned at an angle to a horizontal reference greaterthan zero degrees and wherein the lumen comprises a first end and asecond end and wherein the first end is exposed to atmospheric pressureand wherein the lumen comprises a first known dimension (e.g., thediameter of the first lumen); a flow restrictor (e.g., a capillary tube)having an inlet and an outlet wherein the inlet is coupled to the secondend and wherein the flow restrictor includes some known dimensions(e.g., the length and diameter of the flow restrictor); a valve coupledto the vascular system of the living being at a first port wherein thevalve comprises a second port coupled to the outlet and a third portcoupled to an input of a second lumen (e.g., an adaptor, etc.) arrangedto deliver any blood that passes therethrough to a collector through anoutput of the second lumen; a sensor for detecting the movement of theblood over time (e.g., a mass detector, a column level detector, etc.)through the apparatus and wherein the sensor generates data relating tothe movement of the blood over time; a processor, coupled to the valveand the sensor and wherein the processor is arranged to operate thevalve to create a column of blood in the first lumen and the flowrestrictor and to establish a pressure differential between the firstend and the output wherein the column of blood moves through the lumenand the flow restrictor at a first shear rate caused by the pressuredifferential and wherein the movement of the column of blood causes thepressure differential to decrease from the first shear rate forgenerating the plural shear rates; and wherein the processor calculatesthe viscosity of the blood based on the data relating to the movement ofthe column of blood over time, the first known dimension of the firstlumen and the some known dimensions of the flow restrictor.

DESCRIPTION OF THE DRAWINGS

[0010] The invention of this present application will be readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein:

[0011]FIG. 1 is a block diagram of a single riser/single capillary(SRSC) blood viscometer using mass detection which is also referred toas a mass detection capillary blood viscometer (MDCBV);

[0012]FIG. 1A is a height vs. time plot of the blood column in the risertube of the MDCBV;

[0013]FIG. 1B is a mass vs. time plot of the blood as it is collected inthe collector of the MDCBV;

[0014]FIG. 2 is a front view of an embodiment of the MDCBV;

[0015]FIG. 3 is a side view of the MDCBV;

[0016]FIG. 4 is a functional diagram of the MDCBV;

[0017]FIG. 5A is a functional diagram of the valve activated to create acolumn of blood;

[0018]FIG. 5B is a functional diagram of the valve activated to permitthe column of blood to fall and be collected in a collector;

[0019]FIG. 6 is a functional diagram of a second embodiment of the MDCBVhaving an alternative position of the capillary tube;

[0020]FIG. 7 is a functional diagram of a third embodiment of the MDCBVhaving an alternative position of the valve mechanism;

[0021]FIG. 8A is a functional diagram of the valve mechanism of FIG. 7activated to create a column of blood;

[0022]FIG. 8B is a functional diagram of the valve mechanism of FIG. 7activated to permit the column of blood to move and be collected in acollector;

[0023]FIG. 9 depicts a fourth embodiment of the MDCBV wherein thechanging mass of falling column of blood is detected;

[0024]FIG. 10 depicts the mass vs. time plot the falling column of bloodfor the fourth embodiment of FIG. 9;

[0025]FIG. 11 is a block diagram of a SRSC blood viscometer using acolumn height detector known as a column height detection capillary(CHDC) blood viscometer wherein the changing height of a falling columnof blood is monitored;

[0026]FIG. 12 is a front view of an embodiment of the CHDC bloodviscometer;

[0027]FIG. 13 is a functional diagram of the CHDC blood viscometer;

[0028]FIG. 14 is a functional diagram of a second embodiment of the CHDCblood viscometer having an alternative location of the flow restrictor;and

[0029]FIG. 15 is a functional diagram of a third embodiment of the CHDCblood viscometer having an alternative location of the valve mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention, generally referred to as a singleriser/single capillary (SRSC) blood viscometer, uses a single riser tubeand a single flow restrictor (e.g., a capillary tube) structure fordetermining the viscosity of the circulating blood of a living being.

[0031] Although the SRSC blood viscometer can be implemented in a numberof ways, two exemplary apparatus/methods are set forth below. The firstimplementation uses the SRSC structure along with mass detection andhence is hereinafter referred to as a mass detection capillary bloodviscometer (MDCBV) 20. The second implementation uses the SRSC structurealong with column height detection and hence is hereinafter referred toas a column height detection capillary (CHDC) blood viscometer 1020.

[0032] Referring now in detail to the various figures of the drawingwherein like reference characters refer to like parts, there is shown at920 a mass detecting capillary blood viscometer (MDCBV).

[0033] The MDCBV 920 basically comprises a blood receiver 922 and ananalyzer/output portion 924. The patient is coupled to the MDCBV 920through a circulating blood conveyor 926, e.g., a needle, an IV needle,an in-dwelling catheter, etc., or any equivalent structure that canconvey circulating blood from a patient to the MDCBV 920. As will bediscussed in detail later, the analyzer/output portion 924 provides adisplay 28 for presenting the viscosity information, as well as otherinformation to the operator. The analyzer/output portion 924 may alsoprovide this information to other suitable output means 330, such as adatalogger 332, other computer(s) 334, a printer 336, a plotter 338,remote computers/storage 340, to the Internet 342 or to other on-lineservices 344.

[0034] The blood receiver 922 basically comprises a valve mechanism 946coupled to a riser tube R on one side and coupled to a flow restrictor24 (e.g., a capillary tube) on the other side. The output of the flowrestrictor 24 is directed into a fluid collector 26 via an adaptor 34.When the blood conveyor 926 is coupled to the blood receiver 922, thevalve mechanism 946 controls the flow of blood into the blood receiver922, as will be discussed in detail later. The upper end of the risertube R is exposed to atmospheric pressure. The riser tube R may bepositioned at any non-zero angle to a horizontal reference position(e.g., the datum line as shown in FIG. 4); one exemplary position is ata vertical orientation with respect to the datum line as shown in FIG.4.

[0035] It should be understood that the blood receiver 922 may bedisposable or non-disposable. As will be discussed in detail later,where the blood receiver 922 is disposable, the components (valvemechanism 946, riser tube R and flow restrictor 24) are releasablysecured in a blood receiver housing 962 that can be quickly and easilyinserted, used during the viscosity test run and then quickly and easilyremoved for disposal; another disposable blood receiver 922 is theninserted in preparation for the next viscosity test run. On the otherhand, where the blood receiver 922 is non-disposable, the components(valve mechanism 946, riser tube Rand flow restrictor 24) can bethoroughly washed and cleaned in place in preparation for the nextviscosity test run.

[0036] It should be understood that the flow restrictor 24 does notnecessarily have to be an elongated tube but may comprise a variety ofconfigurations such as a coiled capillary tube.

[0037] The analyzer/output portion 924 basically comprises a massdetector 28, a level detector 400, a processor 30, the display 928, abar code reader 978, an environmental control unit 980, and overflowdetector 981, a first battery B1 and a second back-up battery B2. Thefluid collector 26 is positioned on top of the mass detector 28 whichmonitors the increasing mass of blood collecting in the fluid collector26. The overflow detector 981 ensures that when the column of blood isgenerated, no blood overflows the riser R. The processor 30 (e.g., a“386” microprocessor or greater, or any equivalent) is arranged toanalyze the data from the mass detector 28 and to calculate the bloodviscosity therefrom, as will also be discussed in detail later.Furthermore, the processor 30 also controls the display 928 forproviding the viscosity information and the other information to theoperator as well as to the other output means 330. The processor 30 alsocontrols the valve mechanism 946 based on the data from the massdetector 28, as will be discussed later. Battery B1 provides all of therequisite power to the analyzer/output portion 24, with battery B2serving as a back-up power supply. The bar code reader 978, theenvironmental control unit 980 and the level detector 400 will bedescribed later.

[0038] In general, via the use of the valve mechanism 946, a column ofblood 38 is initially generated in the riser R and then that column ofblood 38 is permitted to fall through the riser tube R, through the flowrestrictor 24 and into the fluid collector 26. This movement of bloodcan be represented by a height vs. time relationship (FIG. 1A) withregard to the column of blood in the riser R and by a mass vs. timerelationship (FIG. 1B) with regard to the blood being received in thefluid collector 26.

[0039] As shown more clearly in FIGS. 2-3, the preferred embodiment ofthe MDCBV 920 comprises the blood receiver 922 and the analyzer/outputportion 924 contained in respective housings 960 and 962, each of whichcan be releasably secured to a common frame, e.g., a conventionalintravenous (IV) pole 48. In this configuration, the analyzer/outputportion 924 can be positioned in an inclined orientation (see FIG. 3) tofacilitate user operation and viewing of the display 928. However, itshould be understood that the respective housing constructions areexemplary, and others can be incorporated without limiting the scope ofthis invention.

[0040] The display 928 may comprise any suitable conventional devices,e.g., an ELD (electroluminescent display) or LCD (liquid crystaldisplay) that permits the visualization of both text and graphics. Theresolution of this display 928 is preferably 800×600 VGA or above.Furthermore, while the preferred embodiment utilizes a touch screendisplay which incorporates, among other things:

[0041] graphical display 961

[0042] instruction, and/or data, display 965 (which also includes thecommand line display shown as “RUN TEST”; e.g., “TESTING”, “TEST INPROGRESS,” etc.)

[0043] alphanumeric keypad 968

[0044] emergency stop button 970

[0045] battery status indicators, 972A and 972B

[0046] function buttons 974,

[0047] it should be understood that any equivalent display device iswithin the broadest scope of the invention. Thus, any number of userinterfaces and buttons may be available through the display 928.Therefore the invention 920 is not limited to the embodiment that isshown in FIG. 2. Moreover, the display 928 can be operated to minimizeor maximize, or overlay any particular graphic or text screen, as isavailable in any conventional object-oriented operating system, such asMicrosoft® WINDOWS.

[0048] The lower housing 960 comprises the blood receiver 922 and themass detector 28. In the preferred embodiment, the mass detector 28 maycomprise a precision balance, or load cell, such as The Adventurer™ byOhaus Corporation of Florham Park, N.J. Thus, as the collector 26collects more of the blood during the viscosity test run, the changingmass value is transmitted to the processor 30 from the mass detector 28for viscosity determination; in particular, the mass detector 28generates an electrical signal that corresponds to the mass variation intime. It should be understood that the term “mass” may be interchangedwith the term “weight” for purposes of this invention. It should also beunderstood that the connection between the mass detector 28 and theprocessor 30 is bi-directional; this allows the processor 30 to resetthe mass detector 28 in preparation for a new test run.

[0049] It should also be understood that although it is preferable tohave the riser tube R in a vertical position, it is within the broadestscope of this invention to have the riser tube R oriented at any anglegreater than zero degrees, with respect to a horizontal reference (e.g.,datum line shown in FIG. 4).

[0050] Where the blood receiver 922 is disposable, it is releasablysecured in the housing 960 such that once a test run is completed and/ora new patient is to be tested, all of the lumens (e.g., the riser tubeR, the capillary 24, the adaptor 34 and the valve mechanism 946) can beeasily/quickly removed, disposed of and a new set inserted. For example,a bracket 147 (FIG. 2) may be used to releasably secure the upperportion of the riser tube R.

[0051] A door 976 (which can be vertically or horizontally hinged to thehousing 960) is provided to establish a temperature-controlledenvironment during the test run. In particular, the door 976 alsosupports an environmental control unit 980 (e.g., a heater, fan and/orthermostat) such that when it is closed in preparation for the test, theflow restrictor 24 is then heated (or cooled) and maintained throughoutthe test run at the same temperature and environment as the livingbeing. Prior to the run, the living being's temperature is taken and theoperator enters this temperature (via the touch screen display 928). Theenvironmental control unit 980 then operates to achieve and maintainthis temperature. It should be noted that it is within the broadestscope of this invention to include a environmental control unit 980 thatachieves and maintains the entire blood receiver 922 at the patient'stemperature during the run. By properly maintaining the temperaturethroughout the test run, the effects of any temperature variation in theviscosity measurement is minimized.

[0052] The door 976 may also support the bar code reader 978. The barcode reader 978 automatically reads a bar code (not shown) that isprovided on the riser tube R. The bar code contains all of thepredetermined data regarding the characteristics of the flow restrictor24 (e.g., its length and diameter) and the characteristics of the risertube R. This information is passed to the processor 30 which is thenused to determine the viscosity.

[0053] The batteries B1/B2 may each comprise a 12 VDC, 4 amp-hourbattery, or any equivalent power supply (e.g., batteries used inconventional lap-top computers such as lithium ion batteries). Thedisplay 928 provides the status indicators 972A/972B for each battery inthe MDCBV 920. In particular, when the MDCBV 920 is operating off ofbattery B1, the two battery indicators 972A/972B appear on the display928. However, once battery B1 is depleted, the battery B1 indicator 972Adisappears and the battery B2 indicator 972B blinks to warn the operatorthat the MDCBV 920 is now operating off of the back-up battery B2 andre-charge of battery B1 is necessary.

[0054] The preferred fluid collector 26 of the present invention issimilar to that disclosed in application Ser. No. 09/789,350. Inparticular, the collector 26 comprises an inner circular wall 35 thatdivides the collector 26 into a central portion 31 and an annularportion 39. The central portion 31 collects the blood as it enters thecollector 26. The column of blood 38 falls through the riser tube R, theflow restrictor 24, the adaptor 34 and then into the central portion 31.Any overflow spills into the annular portion 39.

[0055] It should be understood that the phrase “column of blood 38” ismeant to cover the continuous element of blood that occupies the risertube R as well as the blood that occupies the flow restrictor 24 and theadaptor 34.

[0056] To minimize any surface tension effects that would normally occurif an open end 36 of the adaptor was positioned above the level ofcollected blood 300 in the central portion 31, it is necessary to begincollecting mass vs. time data only when the open end 36 of the adaptor34 is submerged within the collected blood 300. This is shown mostclearly in FIG. 4. In order to accomplish this, the open end 36 of theadaptor 34 is placed appropriately below the datum line (e.g., the topedge 37 of the inner wall 35 of the preferred collector 26) and thelevel detector 400 is provided for detecting when the collected blood300 has reached the datum level. The level detector 400 informs theprocessor 30 when this event has occurred. Thus, the processor 30 isable to determine those mass vs. time data points where surface tensioneffects are minimized. The level detector 400 can be implemented invarious ways known to those skilled in art, e.g., float sensors, tuningfork sensors, ultrasonic sensors, optical sensors, proximity sensors,capacitance sensors, etc. and all of which generate an electrical signalwhen a particular fluid level has been reached. An exemplary sensor isthe ColeParmer EW-20603-22 Capacitive Level Sensor.

[0057] It should be understood that the output side 3 of the flowrestrictor 24 can be integrally formed with the input side 5 of theadaptor 34.

[0058] The concept of the blood viscosity determination using the MDCBV920 is that a portion of the circulating blood of the living being isdiverted from the living being using the blood conveyor 926 into theblood receiver 922 to create a column of blood 38 (FIG. 4) in the risertube R. Next, the column of blood 38 is allowed to fall and collect inthe fluid collector 26 over time, whereby the changing mass of thiscollector 26 is monitored over time. From this mass vs. time data andbased on the characteristics of the flow restrictor 24 and the risertube R, the circulating blood viscosity can be determined. In addition,where the blood exhibits yield stress, τ_(y), a residual amount of thecolumn of blood 38 remains in the riser tube R after a long period oftime at the end of the viscosity test run; furthermore, there aresurface tension effects that also contribute to this residual amount ofthe column of blood 38 as a result of the gas-liquid interface 23 (FIG.4). The height of this residual column of fluid is known as Δh_(∞),where Δh=h(t)−datum level and where h(t) represents the height of thecolumn of blood 38 in the riser tube R at any time; the term h_(∞) (FIG.1A) represents the final height of the column of blood 38 in the risertube R at the end of the test run after a long period of time. As willalso be discussed later, the viscosity determination of the blood can bedetermined using the MDCBV 920 without the need to determine h(t) or theinitial position, h_(i), of the column of blood 38 in the riser tube Rat which data is collected.

[0059] To obtain accurate data, it is important to “wet” all of thelumens, namely, the riser tube R, the valve mechanism 946, the flowrestrictor 24 and the adaptor 34 before data is taken. As a result, inorder to generate the column of blood 38 and then allow it to fall, thevalve mechanism 946 must be operated as follows: When the viscosity testrun is initiated, the processor 30 activates the valve mechanism 946 bycommanding a valve driver 986 (e.g., a 500 mA solenoid, or steppermotor, etc.) which rotates the valve into the position shown in FIG. 5A.This allows the diverted portion of the circulating blood to flow upinto the riser tube R to create the column of blood 38. When theoverflow detector 981 detects a predetermined height, h₀, of the columnof blood 38, the overflow detector 981 informs the processor 30 whichthen commands the valve driver 986 to rotate the valve into the positionshown in FIG. 5B. As a result, the column of blood 38 begins to fallthrough the riser tube R, through the valve mechanism 946, into the flowrestrictor 24, through the adaptor 34 and into the central portion 31 ofthe fluid collector 26. As mentioned earlier, the processor 30 isinformed by the level detector 400 when the open end 36 of the adaptor34 is submerged under the level of the collected blood 300 in order tominimize any surface tension effects. Next, the valve driver 986 iscommanded by the processor 30 into the position shown in FIG. 5C whichhalts all motion of the column of blood 38. The initial position of thecolumn of blood, hi, is thereby established for viscosity determinationpurposes, as will be discussed later. Finally, the processor 30 commandsthe valve driver 986 to rotate the valve into the position shown in FIG.5D and the column of blood 38 begins falling while data is collected.

[0060] The overflow detector 981 may comprise an optical source 981A,e.g., a light emitting diode (LED) and a photodetector 981B fordetecting emitted light from the optical source 981A; once the upper endof the column of blood 38 interrupts the emitted light, thephotodetector 981B informs the processor 30 which operates the valvemechanism 946, as discussed previously. It should be understood thatthis implementation of the overflow detector 981 is exemplary only andthat it is within the broadest scope of this invention to include allmethods of level detection known to those skilled in the art ofdetecting the level of the column of blood 38 in the riser tube R.

[0061]FIG. 6 depicts a second embodiment of the MDCBV 920 wherein theflow restrictor 24 forms the lower end of the riser tube R, rather thanbeing located on the other side of the valve mechanism 946. As a result,the input side 5 of the adaptor 34 is coupled to the valve mechanism946. For proper operation, the datum line needs to be above the inputside 7 of the flow restrictor 24, as shown in FIG. 6. Other than that,the operation of this variation is governed by the same equations forthe first embodiment as will be discussed below.

[0062]FIG. 7 depicts a third embodiment of the MDCBV 920 wherein thevalve mechanism 946′ is positioned at the top of the riser tube R,rather than at the bottom. The advantage of this valve mechanism 946′position is that there is no need to first fill the riser tube R to apredetermined level before proceeding with the test run; instead, inaccordance with the valve mechanism 946′ operation as shown in FIGS.8A-8B, the test run proceeds with the processor 30 commanding the valvedriver 986 to rotate the valve to the position shown in FIG. 8A and thenthe processor 30 stops any more input flow from the blood conveyor 926as shown in FIG. 8B. In particular, as used in this embodiment, theblood conveyor 926 is coupled to the valve mechanism 946′ at a port 763;the top end of the riser tube R is coupled to the valve mechanism 946′at a port 765. The valve mechanism 946′ also includes a vent coupler 762that couples the top of the riser R to a third port 764 that is exposedto atmospheric pressure; thus when the valve is rotated into theposition shown in FIG. 8B, the blood in the riser tube R will flowdownwards. Again, it should be emphasized that to minimize any surfacetension effects, the level detector 400 informs the processor 30 whenthe open end of the adaptor 34 is submerged in the collected blood 300.Other than that, the operation of this variation is governed by the sameequations mentioned previously.

[0063] MDCBV Theory of Operation

[0064] The concept of the blood viscosity determination using the MDCBV920 is based on the discussion of determining the viscosity ofnon-Newtonian fluids, such as blood, as discussed in detail inapplication Ser. No. 09/789,350, whose entire disclosure is incorporatedby reference herein. The MDCBV 920 basically comprises a cylinder (i.e.,the riser tube R) having a diameter, φ_(R), into which a portion of thecirculating blood of the living being is diverted for viscosityanalysis. The bottom of the riser tube R is coupled to the flowrestrictor 24 (e.g., a capillary tube), having a diameter φ_(c) and alength L_(c). It is preferable that the diameter of the adaptor 34 besimilar to the diameter of the riser tube R, φ_(R).

[0065] Using this configuration of riser tube R and flow restrictor 24,once the column of blood 38 is generated (as shown in FIG. 4), when thevalve mechanism 946 is rotated to the position shown in FIG. 5B, thecolumn of blood 38 is subjected to a decreasing pressure differentialthat moves the column 38 through a plurality of shear rates (i.e., froma high shear rate at the beginning of the test run to a low shear rateat the end of the test run, as can be clearly seen in the column heightchange—FIG. 1A and the mass accumulating in the collector 26′—FIG. 1B),which is especially important in determining the viscosity ofnon-Newtonian fluids, such as blood. In particular, once the desiredheight, h_(i) is achieved by the column of blood 38 and with the upperend of the riser tube R exposed to atmospheric pressure, a pressuredifferential is created between the column of fluid 38 and the outlet 36of the adaptor 34. As a result, the column of blood 38 flows down theriser tube R, through the flow restrictor 24, through the adaptor 34 andinto the collector 26′. As the column of blood 38 flows through thesecomponents, the movement of column of blood 38 causes the pressuredifferential to decrease, thereby causing the movement of the column ofblood 38 to slow down. This movement of the column of blood 38,initially at a high shear rate and diminishing to a low shear rate, thuscovers the plurality of shear rates. However, it should be understoodthat it is within the broadest scope of this invention to include anyother configurations where the column of blood 38 can be subjected to adecreasing pressure differential in order to move the column of blood 38through a plurality of shear rates.

[0066] The rate of flow through the flow restrictor 24 is equal to therate of change of the mass of the blood 300 collected on the massdetector 28. Hence, the corresponding flow rate in the flow restrictor24 can be expressed as: $\begin{matrix}{{Q(t)} = {\frac{1}{\rho}\quad \frac{m}{t}}} & (1)\end{matrix}$

[0067] where ρ is the density of the blood.

[0068] In order to determine the viscosity of the blood, it is necessaryto know the pressure drop across the flow restrictor 24. What ismeasured using the MDCBV 20 is the total pressure drop between the risertube R and the flow restrictor 24 including not only the pressure dropacross the flow restrictor or capillary tube 24 (ΔP_(c)) but also thepressure drop occurring at the inlet and outlet (ΔP_(e)) of thecapillary tube 24. One of the accurate methods for determining (ΔP_(e))is to make a Bagley plot (see C. W. Macosko, Rheology: Principles,Measurements, and Applications (VCH, 1993)) with at least two shortcapillary tubes (not shown) of the same diameter. Hence, the pressuredrop occurring at the inlet and at the outlet of the capillary tube 24has to be subtracted from the total pressure difference (ΔP_(t)).Considering these pressure drops, the pressure drop across the capillarytube 24 can be described as

ΔP _(c) =ΔP _(t) −ΔP _(e)   (2)

[0069] It should be noted that the contribution from the second term onthe right hand side (ΔP_(e)) in Eq. (2) is less than 0.5%; hence thisterm can be neglected for all practical purposes, and as a result,equation 2 reduces to:

ΔP _(c) =ΔP _(t)   (3)

[0070] An expression, therefore, for the total pressure as well as thepressure across the capillary tube 24 is:

ΔP _(t) =ΔP _(c) =ρg[h _(i) −Δh(t)−h _(∞) ]=ρg[h _(i) −h _(∞)Δh(t)]  (4),

[0071] where Δh(t) represents the changing height of the falling columnof blood 38 and is given by the following equation: $\begin{matrix}{{\Delta \quad {h(t)}} = \frac{4{m(t)}}{{\rho\pi}\quad \varphi_{R}^{2}}} & (5)\end{matrix}$

[0072] and where:

[0073] h_(i) is the initial height of the column of blood 38;

[0074] h_(∞) is the final height of the column of blood 38 after a longperiod of time; and

[0075] m(t) is the mass of the collector 26 over time.

[0076] In addition, the final mass after a long period of time, m_(∞),can be expressed in terms of the height of the column of blood 38 asfollows: $\begin{matrix}{{{m_{\infty} - m_{i}} = {{\rho \left( \frac{{\pi\varphi}_{R}^{2}}{4} \right)}\quad \left( {h_{i} - h_{\infty}} \right)}};} & (6)\end{matrix}$

[0077] and solving equation 6 for (h_(i)−h_(∞)), $\begin{matrix}{\left( {h_{i} - h_{\infty}} \right) = \frac{4\left( {m_{\infty} - m_{i}} \right)}{{\rho\pi\varphi}_{R}^{2}}} & (7)\end{matrix}$

[0078] Thus, making the substitution of equations 5 and 7 into equation4, $\begin{matrix}\begin{matrix}{{\Delta \quad P_{c}} = {\rho \quad {g\left\lbrack {\frac{4\left( {m_{\infty} - m_{i}} \right)}{{\rho\pi}\quad \varphi_{R}^{2}} - \frac{4{m(t)}}{{\rho\pi\varphi}_{R}^{2}}} \right\rbrack}}} \\{= {\frac{4g}{{\pi\varphi}_{R}^{2}}\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}}\end{matrix} & (8)\end{matrix}$

[0079] It is assumed that any surface tension effects are constant withtime and throughout the test run, e.g., the surface tension experiencedat h_(i) is similar to the surface tension effect experienced at h_(∞).

[0080] The significance of equation 8 includes, among other things, thatin order to determine the pressure across the capillary tube 24, onlythe final mass, m_(∞), the diameter of the riser R and the mass datadetected by the mass detector 28, m(t), need be known; the initialheight of the blood column 38, h_(i), nor the final height, h_(∞), northe initial mass, m_(i), need to be known. Furthermore, equation 8 alsorepresents, in accordance with the assumption that the surface tensionis constant, a surface tension-free capillary.

[0081] Non-Newtonian Fluids

[0082] The shear rate dependent viscosity for a non-Newtonian fluid,such as blood, flowing in the capillary tube 24 is obtained fromexperimental data with some mathematical treatment, and the necessaryequations can be found in any standard handbook (e.g., C. W. Macosko).The shear rate at the capillary tube 24 wall is obtained form theclassical Weissenberg-Rabinowitsch equation (see S. L. Kokal, B. Habibi,and B. B. Maini, Novel Capillary Pulse Viscometer for non-NewtonianFluids, Review of Scientific Instrument, 67(9), pp. 3149-3157 (1996)):$\begin{matrix}\begin{matrix}{{{{\overset{.}{\gamma}}_{w}(t)} = {- \frac{V_{z}}{r}}}}_{r = R} \\{= {\frac{1}{4}{{\overset{.}{\gamma}}_{aw}\left\lbrack {3 + \frac{{\quad \ln}\quad Q}{{\ln}\quad \tau_{w}}} \right\rbrack}}}\end{matrix} & (9)\end{matrix}$

[0083] where {dot over (γ)}_(aw) is the apparent or Newtonian shear rateat the wall and where φ_(c) is the diameter of the capillary tube 24.$\begin{matrix}{{{\overset{.}{\gamma}}_{aw}(t)} = \frac{32\quad {Q(t)}}{{\pi\varphi}_{c}^{3}}} & (10)\end{matrix}$

[0084] and the shear stress at the wall is given by: $\begin{matrix}{{\tau_{w}(t)} = \frac{\Delta \quad {P(t)}\varphi_{c}}{4L_{c}}} & (11)\end{matrix}$

[0085] Thus, the viscosity corresponding to the wall shear rate iscalculated in the form of a generalized Newtonian viscosity:$\begin{matrix}\begin{matrix}{\eta = {\frac{\tau_{w}}{{\overset{.}{\gamma}}_{w}} = {\frac{{\pi\varphi}_{c}^{4}\Delta \quad P}{32{QL}_{c}}\left( {3 + \frac{{\quad \ln}\quad Q}{{\ln}\quad \tau_{w}}} \right)^{- 1}}}} \\{= {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\frac{\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}{\left( \frac{m}{t} \right)\quad \left( {3 + \frac{1}{n^{\prime}}} \right)}}}\end{matrix} & (12)\end{matrix}$

${{where}\quad \frac{1}{n^{\prime}}} = {\frac{{\quad \ln}\quad Q}{{\ln}\quad \tau_{w}}.}$

[0086] Thus, Equation 12 represents the viscosity of the blood in termsof the mass measured by the MDCBV 920.

[0087] The viscosity versus shear rate information can be obtained fromequations 9-12 by measuring the mass of the collected fluid with respectto the time from which the pressure drop and flow rate can becalculated. The values of R and L_(c) must be obtained by calibration.Since equation (9) is non-linear, the procedure to calculate the shearrate and the corresponding viscosity is not straightforward. One of theapproaches to obtain the viscosity from the general equations presentedabove is to adopt a finite difference technique for differentiation ofequation (9). If there is enough data near the point of interest, it ispossible to evaluate the derivative as: $\begin{matrix}{\frac{1}{n^{\prime}} = {\frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}} = \frac{1}{n}}} & (13)\end{matrix}$

[0088] where n is simply the exponent of the power law constitutiveequation. Even though the power-law exponent is used in the aboveequations, this does not limit the capability of the present measurementfor power-law fluids. The rigorous approach can still be taken forobtaining a viscosity versus shear rate relationship for any fluid (seeS. L. Kokal, B. Habibi, and B. B. Maini, “Novel Capillary PulseViscometer for non-Newtonian fluids, Review of Scientific Instrument,67(9), 3149-3157 (1996)).

[0089] In application Ser. No. 09/789,350 there is a figure, namely,FIG. 7, which illustrates the viscosity results using a mass detectorviscometer for blood and which shows an excellent agreement with thosefrom a conventional rotating viscometer, e.g., the Physica UDS-200 overa range of shear rates.

[0090] As mentioned earlier FIGS. 1A and 1B provide a summary of theheight vs. time characteristic, and the mass vs. time characteristic ,of the falling column of blood 38 during the viscosity test run. As canbe seen in FIG. 8A, the level of the column of blood 38 initially is ath_(i). During the test run, the column of blood 38 falls and arrives ata final column height of h_(∞) after a long period of time (e.g., 2-5minutes after the column of blood 38 begins to fall). As also mentionedearlier, this final height h_(∞) can be attributed to both the surfacetension effect of the gas-liquid interface 23 (FIG. 4) as well as anyyield stress, τ_(y), exhibited by the blood. With regard to the changein mass, m(t), as shown in FIG. 8B, the mass climbs quickly and thenslows down towards a final mass value, m_(∞) after a long period oftime. As mentioned earlier, what is important here is that the viscosityof the blood can be determined using the MDCBV 920 without the need toknow h_(i) and h_(∞).

[0091]FIG. 9 depicts a fourth embodiment of the MDCBV 920 wherein thechanging mass of the riser R and flow restrictor 24 are detected, ratherthan detecting the change in mass of the collected blood 300 in thecollector 26. Thus, rather than obtaining an increasing mass with time,the mass detector 28 detects the decreasing mass of the riser R/flowrestrictor 24 assembly with time, as shown in FIG. 10. The empty weightof the riser R, flow restrictor 24 and a base 29 (upon which the flowrestrictor 24 is disposed) are taken into account before the test run isconducted. As a result, the expression for the pressure drop across thecapillary tube 24 is: $\begin{matrix}{{\Delta \quad P_{c}} = {{\frac{4g}{{\pi\varphi}_{R}^{2}}\left\lbrack {\left( {m_{i} - m_{\infty}} \right) - {m(t)}} \right\rbrack}.}} & (14)\end{matrix}$

[0092] Other than that, the theory of operation of this fourthembodiment of the MDCBV 920 is similar to that discussed above withregard to the other embodiments of the MDCBV 920.

[0093] A column height detection capillary (CHDC) blood viscometer 1020is discussed next.

[0094] The CHDC blood viscometer 1020 utilizes the same structure, forexample, the riser tube R and the flow restrictor 24, but with the massdetector 28 and the overflow detector 981 replaced by column leveldetector 1056. As a result, the viscosity of the circulating blood ofthe living being can be determined using the CHDC viscometer 1020. Inparticular, it can be shown that the viscosity of the circulating blood,η, is given by:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\left( \frac{h_{i} - h_{\infty} - {\Delta \quad {h(t)}}}{\frac{{h(t)}}{t}\left( {3 + \frac{1}{n^{\prime}}} \right)} \right)}$

[0095] The column level detector 1056 is similar to the one disclosed inapplication Ser. No. 09/573,267 whose entire disclosure is incorporatedby reference herein. The column level detector 1056 detects the level ofthe column of blood in the riser tube R and may comprise and LED array1064 and a CCD 1066 arrangement (FIG. 12). To that end, the CHDC bloodviscometer 1020 basically comprises the blood receiver 922 and ananalyzer/output portion 1024.

[0096] It should be emphasized that it is within the broadest scope ofthis invention to include all ways known in the art for detecting thelevel of the column of blood and the present invention is not limited,in any way, to the use of optical detection.

[0097] As with the MDCBV 920, the output side 3 of the flow restrictor24 can be integrally formed with the input side 5 of the adaptor 34.

[0098]FIG. 12 depicts one embodiment of the CHDC blood viscometer 1020which operates similarly to the MDCBV 920 except that the level of thecolumn of blood 38 is monitored rather than the changing mass in thecollector 26. In addition, the function of the overflow detector 981 inthe MDCBV 920 is accomplished by the column level detector 1056, therebyinforming the processor 30 when to operate the valve mechanism 960 toallow the column of blood 38 to fall. As a result, the CHDC bloodviscometer 1020 utilizes height vs. time data, as shown in FIG. 1A, todetermine the blood viscosity. FIG. 13 is a functional diagram of theCHDC blood viscometer 1020 that depicts the operation of the CHDC bloodviscometer 1020, including the use of the submerged end 36 of theadaptor 34 and the level detector 400.

[0099]FIG. 14 is a second embodiment of the CHDC blood viscometer 1020wherein the flow restrictor 24 forms the lower end of the riser tube R,rather than being located on the other side of the valve mechanism 946.As a result, the input side 5 of the adaptor 34 is coupled to the valvemechanism 946. For proper operation, the datum line needs to be abovethe input side 7 of the flow restrictor 24, as shown in FIG. 14. Otherthan that, the operation of this variation is governed by the sameequations for the first embodiment of the CHDC blood viscometer 1020 aswill be discussed below.

[0100]FIG. 15 depicts a third embodiment of the CHDC blood viscometer1020 wherein the valve mechanism 946′ is positioned at the top of theriser tube R, rather than at the bottom. The same discussion thatapplies to the third embodiment of the MDCBV 920 that was discussedearlier, applies here for the CHDC blood viscometer 1020.

[0101] Without further elaboration, the foregoing will so fullyillustrate our invention and others may, by applying current or futureknowledge, readily adapt the same for use under various conditions ofservice.

We claim:
 1. An apparatus for determining the viscosity of thecirculating blood of a living being over plural shear rates using adecreasing pressure differential, said apparatus comprising: a lumenbeing positioned at an angle to a horizontal reference greater than zerodegrees, said lumen comprising a first end and a second end, said firstend being exposed to atmospheric pressure, said lumen comprising a firstknown dimension; a flow restrictor having an inlet and an outlet, saidoutlet being arranged to deliver any blood that passes therethrough to acollector, said flow restrictor including some known dimensions; a valvecoupled to the vascular system of the living being at a first port, saidvalve comprising a second port coupled to said second end and a thirdport coupled to said inlet; a sensor for detecting the movement of theblood over time through said apparatus, said sensor generating datarelating to the movement of the blood over time; a processor, coupled tosaid valve and said sensor, said processor arranged to operate saidvalve to create a column of blood in said first lumen and said flowrestrictor and to establish a pressure differential between said firstend and said outlet, said column of blood moving through said lumen andsaid flow restrictor at a first shear rate caused by said pressuredifferential, said movement of said column of blood causing saidpressure differential to decrease from said first shear rate forgenerating said plural shear rates; and wherein said processorcalculates the viscosity of the blood based on said data relating to themovement of the column of blood over time, said first known dimension ofsaid lumen and said some known dimensions of said flow restrictor. 2.The apparatus of claim 1 wherein said outlet remains submerged in theblood that is being collected in said collector when said column ofblood is moving.
 3. The apparatus of claim 2 wherein said sensor detectsthe changing weight of said collector over time as the blood passes fromsaid outlet into said collector.
 4. The apparatus of claim 2 whereinsaid column of blood comprises a level that changes with time, saidsensor detecting said changing level of fluid over time.
 5. Theapparatus of claim 3 wherein said flow restrictor is a capillary tubeand wherein the pressure drop across said capillary tube, ΔP_(c), isgiven by:${\Delta \quad P_{c}} = {\frac{4g}{{\pi\varphi}_{R}^{2}}\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}$

where, g is gravitational acceleration; φ_(R) is the diameter of saidlumen; m_(∞) is the final weight of said collector after a long periodof time; m_(i) is the initial weight of said collector before saidcolumn of blood starts moving; and m(t) is the changing weight of thecollector over time.
 6. The apparatus of claim 5 wherein the viscosity,η, is given by:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\frac{\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}{\left( \frac{m}{t} \right)\left( {3 + \frac{1}{n^{\prime}}} \right)}}$

where, ρ is the density of the blood; φ_(c) is the diameter of saidcapillary tube; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.$


7. The apparatus of claim 6 wherein the quantity $\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 8. Theapparatus of claim 3 wherein said sensor is a precision balance or loadcell.
 9. The apparatus of claim 3 wherein said collector comprises: acontainer having an inner compartment in which said outlet is disposed;and an annular compartment surrounding said inner compartment forforming an overflow chamber.
 10. The apparatus of claim 4 wherein saidflow restrictor is a capillary tube and wherein the pressure drop acrosssaid capillary tube, ΔP_(c), is given by: ΔP _(c) =ρg[h _(i) −h _(∞)−Δh(t)] where: ρ is the density of the blood; g is gravitationalacceleration; h_(i) is the initial height of said column of blood; h_(∞)is the final height of said column of blood; and Δh(t) is the changingheight of said column of blood over time.
 11. The apparatus of claim 10wherein the viscosity of the blood, η, is given by:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\left( \frac{h_{i} - h_{\infty} - {\Delta \quad {h(t)}}}{\frac{{h(t)}}{t}\left( {3 + \frac{1}{n^{\prime}}} \right)} \right)}$

where, φ_(c) is the diameter of said capillary tube; φ_(R) is thediameter of said lumen; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.$


12. The apparatus of claim 11 wherein the quantity$\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 13. Theapparatus of claim 4 wherein said sensor is a column level detector. 14.The apparatus of claim 4 wherein said collector comprises: a containerhaving an inner compartment in which said outlet is disposed; and anannular compartment surrounding said inner compartment for forming anoverflow chamber.
 15. A method for determining the viscosity of thecirculating blood of a living being over plural shear rates caused by adecreasing pressure differential, said method comprising the steps of:(a) providing a lumen having a first end and a second end and positionedat an angle to a horizontal reference greater than zero degrees, saidlumen having a first known dimension, said first end being exposed toatmospheric pressure; (b) diverting a portion of the circulating bloodinto said lumen through said second end to form a column of bloodtherein; (c) coupling an inlet of a flow restrictor to said second endof said lumen to establish a pressure differential between said firstend and said outlet, said flow restrictor having an outlet that isarranged to deliver any blood that passes therethrough to a collector,said flow restrictor having some known dimensions; (d) controlling saidcolumn of blood to form a continuous column of blood in said lumen andsaid flow restrictor, said column of blood moving through said lumen andsaid flow restrictor at a first shear rate caused by said pressuredifferential, said movement of said column of blood causing saidpressure differential to decrease from said first shear rate forgenerating said plural shear rates; (e) providing a sensor for detectingthe movement of the column of blood over time as the column of bloodmoves and passes from said outlet into said collector while maintainingsaid outlet submerged in blood that has collected in said collector,said sensor generating data regarding said movement; and (f) calculatingthe viscosity of the blood based on the generated data, said first knowndimension and said some known dimensions.
 16. The method of claim 15wherein said step of providing a sensor comprises disposing saidcollector on a mass detector and obtaining an initial weight of saidcollector before said column of blood begins moving.
 17. The method ofclaim 16 wherein said mass detector comprises a precision balance or aload cell.
 18. The method of claim 15 wherein said step of providing asensor comprises disposing a column level detector adjacent said lumenfor detecting the changing position of a level of said column of blood.19. The method of claim 16 wherein said flow restrictor is a capillarytube and wherein said step of calculating the viscosity comprisesdetermining the pressure drop across said capillary tube, ΔP_(c),according to:${\Delta \quad P_{c}} = {\frac{4g}{{\pi\varphi}_{R}^{2}}\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}$

where, g is gravitational acceleration; φ_(R) is the diameter of saidlumen; m_(∞) final weight of said collector after a long period of time;m_(i) is the initial weight of said collector before said column ofblood starts moving; and m(t) is the changing weight of the collectorover time.
 20. The method of claim 19 wherein said step of calculatingthe viscosity of the blood comprises determining the viscosity, η, ofthe blood according to:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\frac{\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}{\left( \frac{m}{t} \right)\quad \left( {3 + \frac{1}{n^{\prime}}} \right)}}$

where, ρ is the density of the blood; φ_(c) is the diameter of saidcapillary tube; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.$


21. The method of claim 20 wherein the quantity $\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 22. Themethod of claim 18 wherein said flow restrictor is a capillary tube andwherein said step of calculating the viscosity comprises determining thepressure drop across said capillary tube, ΔP_(c), according to: ΔP _(c)=ρg(h _(i) −h _(∞) −Δh(t)) where, ρ is the density of the fluid; g isgravitational acceleration; h_(∞) is the final height of said column ofblood after a long period of time; h_(i) is the initial height of saidcolumn of blood before said column of blood starts moving; and h(t) isthe changing weight of the collector over time.
 23. The method of claim22 wherein said step of calculating the viscosity of the blood comprisesdetermining the viscosity, η, of the blood according to:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\left( \frac{h_{i} - h_{\infty} - {\Delta \quad {h(t)}}}{\frac{{h(t)}}{t}\left( {3 + \frac{1}{n^{\prime}}} \right)} \right)}$

where, φ_(c) is the diameter of said capillary tube; φ_(R) is thediameter of said lumen; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; and$\tau_{w}\quad {is}\quad {\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.}$


24. The method of claim 23 wherein the quantity $\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 25. Anapparatus for determining the viscosity of the circulating blood of aliving being over plural shear rates using a decreasing pressuredifferential, said apparatus comprising: a lumen being positioned at anangle to a horizontal reference greater than zero degrees, said lumencomprising a first end and a second end, said lumen comprising a firstknown dimension; a flow restrictor having an inlet and an outlet, saidoutlet being arranged to deliver any blood that passes therethrough to acollector, said inlet being coupled to said second end, said flowrestrictor including some known dimensions; a valve coupled to thevascular system of the living being at a first port, said valvecomprising a second port coupled to said first end; a sensor fordetecting the movement of the blood over time through said apparatus,said sensor generating data relating to the movement of the blood overtime; a processor, coupled to said valve and said sensor, said processorarranged to operate said valve to create a column of blood in said firstlumen and said flow restrictor and to establish a pressure differentialbetween said first end and said outlet, said column of blood movingthrough said lumen and said flow restrictor at a first shear rate causedby said pressure differential, said movement of said column of bloodcausing said pressure differential to decrease from said first shearrate for generating said plural shear rates; and wherein said processorcalculates the viscosity of the blood based on said data relating to themovement of the column of blood over time, said first known dimension ofsaid lumen and said some known dimensions of said flow restrictor. 26.The apparatus of claim 25 wherein said outlet remains submerged in theblood that is being collected in said collector when said column ofblood is moving.
 27. The apparatus of claim 26 wherein said sensordetects the changing weight of said collector over time as the bloodpasses from said outlet into said collector.
 28. The apparatus of claim26 wherein said column of blood comprises a level that changes withtime, said sensor detecting said changing level of fluid over time. 29.The apparatus of claim 27 wherein said flow restrictor is a capillarytube and wherein the pressure drop across said capillary tube, ΔP_(c),is given by:${\Delta \quad P_{c}} = {\frac{4g}{{\pi\varphi}_{R}^{2}}\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}$

where, g is gravitational acceleration; φ_(R) is the diameter of saidlumen; m_(∞) is the final weight of said collector after a long periodof time; m_(i) is the initial weight of said collector before saidcolumn of blood starts moving; and m(t) is the changing weight of thecollector over time.
 30. The apparatus of claim 29 wherein theviscosity, η, is given by:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\frac{\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}{\left( \frac{m}{t} \right)\quad \left( {3 + \frac{1}{n^{\prime}}} \right)}}$

where, ρ is the density of the blood; φ_(c) is the diameter of saidcapillary tube; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.$


31. The apparatus of claim 30 wherein the quantity$\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 32. Theapparatus of claim 27 wherein said sensor is a precision balance or loadcell.
 33. The apparatus of claim 27 wherein said collector comprises: acontainer having an inner compartment in which said outlet is disposed;and an annular compartment surrounding said inner compartment forforming an overflow chamber.
 34. The apparatus of claim 29 wherein saidflow restrictor is a capillary tube and wherein the pressure drop acrosssaid capillary tube, ΔP_(c), is given by: ΔP _(c) =ρg[h _(i) −h _(∞)Δh(t)] where: ρ is the density of the blood; g is gravitationalacceleration; h_(i) is the initial height of said column of blood; h_(∞)is the final height of said column of blood; and Δh(t) is the changingheight of said column of blood over time.
 35. The apparatus of claim 34wherein the viscosity of the blood, η, is given by:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\left( \frac{h_{i} - h_{\infty} - {\Delta \quad {h(t)}}}{\frac{{h(t)}}{t}\left( {3 + \frac{1}{n^{\prime}}} \right)} \right)}$

where, φ_(c) is the diameter of said capillary tube; φ_(R) is thediameter of said lumen; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\quad \ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; and$\tau_{w}\quad {is}\quad {\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.}$


36. The apparatus of claim 35 wherein the quantity$\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 37. Theapparatus of claim 28 wherein said sensor is a column level detector.38. The apparatus of claim 28 wherein said collector comprises: acontainer having an inner compartment in which said outlet is disposed;and an annular compartment surrounding said inner compartment forforming an overflow chamber.
 39. A method for determining the viscosityof the circulating blood of a living being over plural shear ratescaused by a decreasing pressure differential, said method comprising thesteps of: (a) providing a lumen having a first end and a second end andpositioned at an angle to a horizontal reference greater than zerodegrees, said lumen having a first known dimension; (b) coupling aninlet of a flow restrictor to said second end and arranging an outlet ofsaid flow restrictor to deliver any blood that passes therethrough to acollector, said flow restrictor having some known dimensions; (c)diverting a portion of the circulating blood into said lumen throughsaid first end to form a column of blood in said lumen and said flowrestrictor and to establish a pressure differential between said firstend and said outlet; (c) exposing said first end to atmospheric pressureto cause said column of blood to move through said lumen and said flowrestrictor, said movement of said column of blood causing said pressuredifferential to decrease from said first shear rate for generating saidplural shear rates; (d) providing a sensor for detecting the movement ofthe column of blood over time as the column of blood moves and passesfrom said outlet into said collector while maintaining said outletsubmerged in blood that has collected in said collector, said sensorgenerating data regarding said movement; and (e) calculating theviscosity of the blood based on the generated data, said first knowndimension and said some known dimensions.
 40. The method of claim 39wherein said step of providing a sensor comprises disposing saidcollector on a mass detector and obtaining an initial weight of saidcollector before said column of blood begins moving.
 41. The method ofclaim 40 wherein said mass detector comprises a precision balance or aload cell.
 42. The method of claim 39 wherein said step of providing asensor comprises disposing a column level detector adjacent said lumenfor detecting the changing position of a level of said column of blood.43. The method of claim 40 wherein said flow restrictor is a capillarytube and wherein said step of calculating the viscosity comprisesdetermining the pressure drop across said capillary tube, ΔP_(c),according to:${\Delta \quad P_{c}} = {\frac{4g}{{\pi\varphi}_{R}^{2}}\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}$

where, g is gravitational acceleration; φ_(R) is the diameter of saidlumen; m_(∞) is the final weight of said collector after a long periodof time; m_(i) is the initial weight of said collector before saidcolumn of blood starts moving; and m(t) is the changing weight of thecollector over time.
 44. The method of claim 43 wherein said step ofcalculating the viscosity of the blood comprises determining theviscosity, η, of the blood according to:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\frac{\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}{\left( \frac{m}{t} \right)\quad \left( {3 + \frac{1}{n^{\prime}}} \right)}}$

where, ρ is the density of the blood; φ_(c) is the diameter of saidcapillary tube; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\quad \ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.$


45. The method of claim 44 wherein the quantity $\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 46. Themethod of claim 42 wherein said flow restrictor is a capillary tube andwherein said step of calculating the viscosity comprises determining thepressure drop across said capillary tube, ΔP_(c), according to: ΔP _(c)=ρg(h _(i) −h _(∞) −Δh(t)) where, ρ is the density of the fluid; g isgravitational acceleration; h_(∞) is the final height of said column ofblood after a long period of time; h_(i) is the initial height of saidcolumn of blood before said column of blood starts moving; and h(t) isthe changing weight of the collector over time.
 47. The method of claim46 wherein said step of calculating the viscosity of the blood comprisesdetermining the viscosity, η, of the blood according to:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\left( \frac{h_{i} - h_{\infty} - {\Delta \quad {h(t)}}}{\frac{{h(t)}}{t}\left( {3 + \frac{1}{n^{\prime}}} \right)} \right)}$

where, φ_(c) is the diameter of said capillary tube; φ_(R) is thediameter of said lumen; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.$


48. The method of claim 47 wherein the quantity $\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 49. Anapparatus for determining the viscosity of the circulating blood of aliving being over plural shear rates using a decreasing pressuredifferential, said apparatus comprising: a first lumen being positionedat an angle to a horizontal reference greater than zero degrees, saidlumen comprising a first end and a second end, said first end beingexposed to atmospheric pressure, said lumen comprising a first knowndimension; a flow restrictor having an inlet and an outlet, said inletcoupled to said second end, said flow restrictor including some knowndimensions; a valve coupled to the vascular system of the living beingat a first port, said valve comprising a second port coupled to saidoutlet and a third port coupled to an input of a second lumen arrangedto deliver any blood that passes therethrough to a collector through anoutput of said second lumen; a sensor for detecting the movement of theblood over time through said apparatus, said sensor generating datarelating to the movement of the blood over time; a processor, coupled tosaid valve and said sensor, said processor arranged to operate saidvalve to create a column of blood in said first lumen and said flowrestrictor and to establish a pressure differential between said firstend and said output, said column of blood moving through said lumen andsaid flow restrictor at a first shear rate caused by said pressuredifferential, said movement of said column of blood causing saidpressure differential to decrease from said first shear rate forgenerating said plural shear rates; and wherein said processorcalculates the viscosity of the blood based on said data relating to themovement of the column of blood over time, said first known dimension ofsaid first lumen and said some known dimensions of said flow restrictor.50. The apparatus of claim 49 wherein said inlet of said flow restrictoris positioned at an elevation that is lower than the elevation of saidoutput of said second lumen.
 51. The apparatus of claim 50 wherein saidoutlet remains submerged in the blood that is being collected in saidcollector when said column of blood is moving.
 52. The apparatus ofclaim 51 wherein said sensor detects the changing weight of saidcollector over time as the blood passes from said outlet into saidcollector.
 53. The apparatus of claim 51 wherein said column of bloodcomprises a level that changes with time, said sensor detecting saidchanging level of fluid over time.
 54. The apparatus of claim 52 whereinsaid flow restrictor is a capillary tube and wherein the pressure dropacross said capillary tube, ΔP_(c), is given by:${\Delta \quad P_{c}} = {\frac{4g}{{\pi\varphi}_{R}^{2}}\left\lbrack {m_{\infty} - {m(t)}} \right\rbrack}$

where, g is gravitational acceleration; φ_(R) is the diameter of saidlumen; m_(∞) is the final weight of said collector after a long periodof time; m_(i) is the initial weight of said collector before saidcolumn of blood starts moving; and m(t) is the changing weight of thecollector over time.
 55. The apparatus of claim 54 wherein theviscosity, η, is given by:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\frac{\left\lbrack {m_{\infty} - m_{i} - {m(t)}} \right\rbrack}{\left( \frac{m}{t} \right)\quad \left( {3 + \frac{1}{n^{\prime}}} \right)}}$

where, ρ is the density of the blood; φ_(c) is the diameter of saidcapillary tube; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}}.$


56. The apparatus of claim 55 wherein the quantity$\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 57. Theapparatus of claim 52 wherein said sensor is a precision balance or loadcell.
 58. The apparatus of claim 52 wherein said collector comprises: acontainer having an inner compartment in which said outlet is disposed;and an annular compartment surrounding said inner compartment forforming an overflow chamber.
 59. The apparatus of claim 53 wherein saidflow restrictor is a capillary tube and wherein the pressure drop acrosssaid capillary tube, ΔP_(c), is given by: ΔP _(c) =ρg[h _(i) −h _(∞)−Δh(t)] where: ρ is the density of the blood; g is gravitationalacceleration; h_(i) is the initial height of said column of blood; h_(∞)is the final height of said column of blood; and Δh(t) is the changingheight of said column of blood over time.
 60. The apparatus of claim 59wherein the viscosity of the blood, η, is given by:$\eta = {\frac{\rho \quad g\quad \varphi_{c}^{4}}{8L_{c}\varphi_{R}^{2}}\left( \frac{h_{i} - h_{\infty} - {\Delta \quad {h(t)}}}{\frac{{h(t)}}{t}\left( {3 + \frac{1}{n^{\prime}}} \right)} \right)}$

where, φ_(c) is the diameter of said capillary tube; φ_(R) is thediameter of said lumen; L_(c) is the length of said capillary tube; and${\frac{1}{n^{\prime}} = \frac{{\ln}\quad Q}{{\ln}\quad \tau_{w}}},$

 where Q is the volumetric flow rate through said capillary tube; andτ_(w) is $\frac{\Delta \quad P_{c}\varphi_{c}}{4L_{c}},$


61. The apparatus of claim 60 wherein the quantity$\frac{1}{n^{\prime}}$

can be approximated by $\frac{1}{n}$

where n is the exponent of a power law constitutive equation.
 62. Theapparatus of claim 53 wherein said sensor is a column level detector.63. The apparatus of claim 53 wherein said collector comprises: acontainer having an inner compartment in which said outlet is disposed;and an annular compartment surrounding said inner compartment forforming an overflow chamber.